Question

我有一个带有Express和mysql的NodeJS。我已经放了一个Generic sql函数，所以我多次调用它：

exports.selectCommand=function(table,cols,cond){
    var connection = mysql.createConnection({
        host     : hostname,
        database: databasename,
        user     : username
    });
    try{
        connection.query("SELECT "+cols+" As data from "+table+" where "+cond+" ", function(err, rows, fields) {
            if (err) return "sorry, an error accoured. Please try again later";
            if(rows.length!=0){
            cmd = rows[0].data.toString();
            }
        });
    }catch (e){console.log(e.message);}
    connection.end();
    return cmd; };

我发送了查询，但问题是它返回我发送的第一个查询。

我已将上述功能放在另一个文件中，我称之为：

var db=require('./db.js');
..........
exports.psModel=function(){
    var cmddata="";
    cmddata=db.selectCommand("cmd","value","cmd='textbox'");
}

Answer 1

您的return cmd可能在处理查询之前返回。该调用是异步的。尝试将return语句放在回调中（以及连接端）。像这样：

try{
    connection.query("SELECT "+cols+" As data from "+table+" where "+cond+" ",
        function(err, rows, fields) {
            connection.end();
            if (err) return "sorry, an error occurred. Please try again later";
            if(rows.length!=0){
              cmd = rows[0].data.toString();
              return cmd;
            }
        });
    }catch (e){console.log(e.message);}

带有mysql的NodeJS返回第一个查询结果

1 个答案: